A. Field of the Invention
The present invention relates to a novel endoscope or an optical large view endoscopic system with improved depth perception. In particular, a multiple viewpoint endoscope system comprising a multiple viewpoint camera setup and/or an intelligent or cognitive image control system and display device particularly adapted for localising internal structures within a cavity or an enclosing structure, such as an animal body, for instance the abdomen of an animal or human, or for localising a real or synthetic image of such internal structures within an overview image or on an overview 3D model.
B. Description of the Related Art
Endoscopy refers to techniques used to inspect or to look into internal cavities or hollow structures. Endoscopy is used today for medical applications and for industrial applications such as for instance in the visual inspection of aircraft, diesel and automotive engines by so called borescopes (boroscopes). In the medical field endoscopes are used for life saving inspections and interventions such as endoscopic surgery on organs in a patient's body cavity. Borescopes allow preventive maintenance or inspection work where the area to be inspected is inaccessible by other means. They can for instance be used for preventive maintenance and inspection tasks on targets within an enclosed structure such as aircraft engines and others which require particular attention because of safety requirements. In the remainder of this text only the medical field will be used to illustrate the new apparatus. Its applicability, however, extends without limitations to the industrial working domain.
Medical endoscopic surgery, also called minimal access surgery has become widely used over the last decade because of clear-cut advantages such as a decreased postoperative morbidity, less pain and a shorter hospitalisation. Endoscopic surgery, however, is technically more demanding than ‘classical open surgery’ for several reasons such as smaller instruments, and the limitation of the smaller entry ports. The learning curve of endoscopic surgery is much longer than expected a decade ago.
A crucial problem remains the monocular vision with limited depth perception, together with a small field of view also referred to as ‘tunnel vision’. Normally surgeons work with a camera acquiring video data through the endoscope, and perform surgery on a video display. This causes most depth of vision cues to be lost. The small field of view leads to difficulties of orientation and surgical mistakes. Experimentally, we were able to demonstrate in a rabbit nephrectomy model that the duration of surgery, bleeding and accidents increase when the fields of view becomes smaller. This increase in duration of surgery and in accidents as a consequence of the small field of view decreases with the experience of the surgeon, suggesting that with experience and training the human brain is capable of reconstructing to a certain extent a broader field of view from the video data given. Unexperienced surgeons perceive this problem much more since they are not able to mentally reconstruct such an overview of the working field. Another limitation of the small field of view is the difficulty to position instruments into the field of view: surgery is performed with the lens at a short distance of the target tissue, eg 2 to 3 cm in order to obtain a sharp enlarged image. To position an instrument “blindly” in this field of view requires a lot of experience and training. The alternative is to zoom out to visualize the instrument and then to zoom in again maintaining the instrument in the field of view. It is obvious, that this requires time, slowing down the surgery. During emergency cases eg an important bleeding, this becomes crucial: the artery should be clamped within seconds with the camera at short distance for visualization. If this fails, the operating field is flooded with blood, making things more difficult. This is the main reason why in gynaecologic surgery, for hysterectomies the conversion rates (ie to change from laparoscopy to laparotomy) range from 0 to 30% according to the experience of the surgeon.
Implementations of non-monocular vision through an endoscope are in general embodied as a stereo setup. Two nearby optical pathways provide a baseline and therefore show two different real, but nearby viewpoints. If presented respectively to the left and right eye, this leads to depth perception for a human observer. However, this approach has several drawbacks, like ego the need for an endoscope with a larger cross section or with smaller optical pathways. Moreover, stereoscopic visualization has no transparent implementation yet and requires eg shutter glasses, auto-stereoscopic displays or head mounted displays. Today these approaches to 3D visualization have failed to become widely accepted in endoscopic surgery because too cumbersome and too expensive without real demonstrable benefits.
The limitation of a restricted view has been addressed historically by building wide angle lenses. These have the drawback, however, that a close up view can only be obtained with the lens at a short distance from the tissue, thus making the working distance, i.e. the distance between lens and tissue limited. Another approach is by using with the endoscopes a varifocal camera unit or by using lenses with different focal lengths. This provides a surgeon with an optical zoom, and allows to restrict or enlarge the working field. However, zooming and refocusing is not straightforward per-operatively and is no real option to get a quick overview of the scene. Indeed if one hand holds a camera with a lens, a second hand is needed to adjust the angle of view; this second hand thus is no longer available for surgery. A zoomed out camera view—even if used with larger monitors—is not practical to work with.
The problem thus narrows down to the dilemma, that we need a high resolution essential to work. This requires either a wide angle at short distance or a narrow view at larger distance. The former solution limits the working space, the latter solution makes an overview picture practically impossible. Today lenses and camera units with a variable field of view exist but are not really used for practical reasons.
More recently so called ‘capsule endoscopy’ has been introduced. This technique normally refers to the concept of ‘a camera in a pill’. The device is swallowed and travels independently the internal digestive system. During this passage video data (and eventually supplementary data) are being collected and either stored in local memory or send to a receiver using a wireless link. One of the promoter applications of this technique is the inspection of the small intestine eg to check whether anemia could be caused by intestinal bleeding.